Due to the propensity of malignant tumors to metastasize through the lymphatic system, it has in the past been normal practice in some situations to remove all lymph nodes potentially harboring malignant cells metastasized from a tumor. Recently, the technique of interoperative lymphatic mapping has taken much of the guesswork out of determining which lymph nodes to remove. The at least one lymph node (typically 1-3 lymph nodes) which is the first to receive lymphatic drainage from the tumor (i.e., the sentinel node) is identified and biopsied. If the at least one sentinel node is free of malignant cells, then further lymph node biopsies can be avoided.
Sentinel nodes have been identified by injecting a marking agent into the tumor-bearing tissue and tracing the pathway of the marking agent through the lymphatic system. Visible marking agents have been employed to visually detect sentinel nodes with the naked eye, but such methods typically require significant surgical dissection to view the potential sentinel nodes and detect the presence of marking agent therein. Radioactive isotopes have also been employed as sentinel node marking agents. See, e.g., Kapteijn et al., "Localizing the sentinel node in cutaneous melanoma: gamma probe detection versus blue dye," 4(2) Ann. Surg. Oncol. 156-60 (Mar. 1997) and U.S. Pat. No. 5,732,704 to Thurston et al. These techniques comprise injecting radioactive isotope compositions into the tumor bearing tissue and detecting the migration of the composition from the tumor and into the lymphatic system.
Although such radiochemistry techniques are an improvement over prior visible detection methods in that radioactive marking agents can be detected transcutaneously (regardless of the depth of the sentinel node within the tissue), radiochemistry techniques are less than ideal in a number of aspects. Patients and medical personnel are exposed to potentially harmful doses of ionizing radiation. Radioactive isotopes also pose environmental contamination and disposal issues.
Thus, there has been a need for a method of transcutaneously identifying a sentinel node without using radioactive isotopes.
All references cited herein are incorporated herein by reference in their entireties.